The invention relates to super-oscillatory lens apparatus and methods.
The last decade has seen numerous efforts to achieve imaging resolution beyond that of the Abbe-Rayleigh diffraction limit, which proscribes the visualization of features smaller than about half of the wavelength of light with optical instruments. The main direction of research aiming to break this limit seeks to exploit the evanescent components containing fine detail of the electromagnetic field distribution.
Scanning near-field optical microscopy (SNOM) has been well developed since the work of Betzig on optical fiber tips in the early 1990's [1, 2]. Other near-field imaging techniques have also been developed. Near-field imaging techniques exploit evanescent fields so require samples to be positioned very close to a scanning tip which makes the imaging process very difficult to achieve compared with conventional far-field optics.
More recently a proposal has been made by Zheludev, Huang and co-workers for achieving imaging resolution beyond that of the Abbe-Rayleigh diffraction limit away from the near-field by using an optical mask to modulate a spatially coherent optical field in amplitude and/or phase [3]. The optical mask is defined so as to create constructive interference of waves known as super-oscillation. Super-oscillation leads to a sub-wavelength focus in a field of view beyond the evanescent region.